Deep combustion radiant surfaces with special slotting



M. PARTIOT 3,321,000

DEEP COMBUSTION RADIANT SURFACES WITH SPECIAL SLOTTING May 23, 1967Original Filed June 1'7. 1960 ga /fa? INVENT OR Maurice Pam'or BY Hula,54 t ATTORNEY S United States Patent,

3,321,939 DEEP CUMBUSTIQN RADIANT SURFACEE WITH SlECliAlL SLQTTINGMaurice Partiot, 12 Rue du Plateau Saint-Antoine, Le Chesnay, FranceOriginal application June 17, 1960, Ser. No. 36,767, new

Patent No. 3,179,1d5, dated Apr. 29, 1965. Divided and this appiicationMar. 17, 1965', Ser. No. 44fl,4t55

22 Claims. (Cl. 153-116) This application is a division of my copendingapplication Ser. No. 36,767, filed June 17, 1960, now Patent No.3,179,155 and concerns the design of radiant ceramic plate so that theflame produced by the combustion of flammable gas mixtures is caused topenetrate to a controlled depth in the combustion surface of the ceramicand provide a combustion region of predetermined thickness.

It is an object of this invention to provide means to achievepractically complete combustion of a gaseous mixture by reverberation ofthe radiant energy of combustion.

It is an object of this invention to raise the temperature of theradiant combustion face of a ceramic plate to maximize the rate andcompleteness of combustion of a gaseous mixture.

It is an object of the invention to provide a combustion region ofcontrolled depth below the outer radiant surface of a ceramic plate.

It is an object of the invention to provide a radiant ceramic platehaving holes therethrough for the supply of a combustible gaseousmixture with outer radiant face slotted between holes to provide acombustion region of controlled depth.

It is an object of the invention to provide suflicient space Within thecombustion region to allow for the expansion of combustible gaseswithout an increase in velocity which would drive them out of thecombustion Zone before they have finished burning and at the same timeprovide sufficient velocity to support the Coanda effect which causesthe combustion gases to follow closely the surface of the ceramic platearound a bend.

It has been found that combustion in a radiant surface plate providedwith holes, but unslotted, is confined to a region which begins aboutone thirty-second of an inch Wis") to one sixteenth of an inch GA belowthe radiant surface. As discussed above, this is not quite suflicient toprovide the depth of combustion region needed to produce the fullbenefits of the invention. In order to obtain the desired increasedtemperature of the surface and the more complete oxidation of thegaseous mixture, a deeper combustion region about one sixteenth of aninch to one quarter inch A") thick is provided. With holes or passagesof about one square millimeter in crosssectional area, a slot of about0.7 millimeter to one millimeter in Width and joining rows of holespermits combustion to occur at the bottom of the slot. As a result, anincreased amount of heat is transferred to the material of the ceramicplate, increasing its temperature and both the rate and completeness ofthe combustion of the gaseous mixture.

Several arrangements are proposed, according to the purpose described,and are best adapted to meet variable gas mixture compositions undervaried pressure feed at the gas injector nozzle.

In general, in each of the several arrangements, the upper radiantsurface defines a plurality of hollows, i.e. indentations, cavities orslots, which extend below the radiant surface a depth in excess of theminimum crosssectional dimension of any passage and with a plurality ofsaid passages opening into each hollow, the novel construction resultingin combustion deeply within the hol- Patented May 23, 1967 lows toprovide thereby a substantially hotter radiant surface.

One disposition consists in joining all the holes or passages in any ofone or more rows of such passages at the radiant surface of the plate bya slot which may be three to four millimeters deep and from five-tenthsto eight-tenths of a millimeter wide. The flame will reach deeper intothe holes joined by such a slot, and the wider the slot the deeper theflame will reach inside the slot to heat the side walls of said slotsand to cause said walls to reverberate heat to each other.

In the extreme width case, the flame reaches the bottom of the slot andburns at that level corresponding to the unslotted part of the holes.The flame does not penetrate further into the plate because the designof the holes and the nature of the ceramic are planned to stop the flamefrom backfiring.

In another embodiment of this invention, each slot or cavity is sodisposed as to join, at the bottom of the slot or cavity, passages whichare respectively associated with different rows of such passages. Morespecificalliy, each of the generally opposing side walls forming a partof any one slot or cavity intersects one or more of the passages belowthe radiant surface of the grid and cuts away a por tion of thepassage-defining wall most deeply on that portion thereof which nears anopposing wall of the slot or cavity. This results in a tendency for thegas mixture passing through such intersected passage to be directed atleast in part away from the axis of the passage and in a directiongenerally toward an opposing Wall of the slot or cavity. Such aconstruction results in deep combustion within the slots or cavities andin a much higher radiant temperature of the Walls of the slots orcavities because of the mutually radiant reverberation that takes place.

Other objects will appear from the following description and from thedrawings, in which like numerals refer to like parts throughout:

FIGURE 1 is a fragmentary sectional view of a deep combustion radiantslotted plate having blind holes opened by slots.

FIGURE 2 is a fragmentary sectional view of a deep combustion radiantslotted plate having slotted blind holes and open holes in alternaterows.

FIGURE 3 is a fragmentary plan view of a plate according to theinvention with blind holes and cross bevels to increase heat exchange orreverberation.

FIGURE 4 is a section taken along line 1--1 of FIG- URE 3.

FIGURE 1 shows in a ceramic plate 1 the use of partly blind holes 2.that are aligned in rows and which are cut open and joined by slots 3.Blind holes that are cut open by a slot create turbulence and aid inlocating the combustion region at a predetermined depth. Slots 3 connectwith the outer surface of plate 1 through an outer wider slot 4providing space for expansion of the heated gases. Said slots can have abeveled opening and be of a non continuous design.

In FIGURE 2 the use of slotted blind holes is employed in alternate rowswith intermediate rows of straight bore open holes.

FIGURES 3 and 4 show two adjacent rows of blind holes 5 joined by widerslot 6 with a beveled opening 7. The surface of the plate 8 maypreferably be formed with cross bevels 9 to increase heat exchange andalso allow for heated gas expansion Without substantial velocityincrease thus reducing any tendency of the hot gases to drive themselvesaway from the radiant surface.

In prior constructions of radiant plates there has been a tendency tolet a good part of the heat of combustion be carried away from therefractory plate which is intended to be heated to a maximum degree toconvert as much of the heat of combustion into radiant heat as possible,leaving a minimum to be carried away by convection of the gas. Withprevious constructions the expansion of the gas during combustionimparts away from the plate a relatively high velocity to the exhaustgas which is especially noticeable at the low gas feed pressuresemployed and the resulting low radiation output. One purpose of theinvention is to provide enough space to permit expansion of the burninggas without substantial increase in velocity of flow, which rather staysthe same or decreases. To that effect, the velocity of exhaust gases ispreferably adjusted to follow closely the surface of the ceramic aroundthe bend, or profiles of the indentations, slots of cavities below theouter boundary surface of the plate. In the embodiment in FIGURES 3 and4, the resultant deflection of gases through a side-cut slot causes thecombustion gases to slow down and follow closely the profile of theopposite slot wall, thus enhancing the heat exchange and radiantperformance of the plate.

In the embodiment of FIGURES 3 and 4, the shoulders 31 increase theturbulence of the gas mixture within the combustion region and helpassure completeness of the combustion. Similarly, in the embodiments ofFIGURES l and 2, a restriction or obturation is provided in the path ofthe gas stream prior to its issuance into the outer wider slots providedat the combustion surface. For example, in FIGURE 1, the narrow slots 3provide an obturation encountered by the gas mixture passing upwardlythrough each blind hole 2 and prior to its emergence into the widerouter slot 3a. In FIGURE 2, the use of a narrow slot 3 intersecting thepassages 2 of alternate rows provides a restriction 4a encountered byeach streamlet of the gas mixture just prior to its emergence into thewider slot 4 at the combustion surface. In each case, such an obturationforming a restriction in the flow path of the gas mixture prior to itsemergence into the associated indentation increases the velocity of thegas mixture at least near the outlet of such restriction and therebyincreases substantially its turbulence in the expanded space adjacentthe outlet end of the restriction.

While there have been described above what are presently believed to bethe preferred form of the invention,

variations thereof will be obvious to those skilled in the art and allsuch changes and variations which fall within the spirit of theinvention are intended to be covered by the generic terms in theappended claims, which are variably worded to that end.

I claim:

1. A radiant grid element for a gas burner comprising, a unitary blockof refractory heat insulating material having a myriad of continuous,straight minute-bore passages which extend from an inlet end at a firstboundary surface of said block toward the opposite surface of said blockfor conductingfrom said first surface a myriad of streams of acombustible gas mixture for combustion ad jacent said opposite surface,said block having formed in its said opposite surface a repeat patternof indentations each of which intersects at least two of said passages,each said intersected pass-age together with the respective intersectingindentation forming a restriction in the flow path of said gas mixtureprior to its emergence into the associated indentation to therebyincrease the velocity of said gas mixture in said restriction and impartto said gas mixture at turbulence adjacent the outlet end of saidrestriction, the arrangement of said passages and their dimensionstogether with the shape and size of said indentations comprising a meanswhich is jointly operable to cause at least someof the gas mixture toburn at substantially the outlet ends of the respective restrictions,the thickness of said block at its minimum within said indentations andthe nature of the refractory material of said block comprising a meanswhich is jointly operable to prevent said first surface from reachingthe ignition temperature of said gas mixture, and each said passagebeing many times longer than its width and sufficiently narrow toprevent the flame from back-propagating therethrough to said firstsurface.

2. The radiant grid element of claim 1 in which each said indentationcomprises an elongate slot.

3. The radiant grid element of claim 2 in which each slot has a Widthless than the major cross-sectional dimension of each said minute-borepassage.

4. The radiant grid element of claim 2 in which each said slot has awidth at the level of its intersection with the associated passageswhich is less than the maximum cross-sectional dimension of theintersected passages but but has a substantially greater width at saidopposite surface.

5. The radiant grid element of claim 2 in which the opposing walls ofsaid slot are substantially planar.

6. The radiant grid element of claim 1 in which at least some of saidindentations have opposing peripheral wall surfaces which aresubstantially parallel inthe area adjacent to the intersection of saidindentation with said passages but thereafter diverge in the regionadjacent the furthest reaches of said opposite surface.

7. The radiant grid element of claim 1 in which each said intersectedpassage comprises a blind hole and each intersecting indentation extendsfrom said opposite surface downwardly below the level of saidrestriction.

8. The ceramic block of claim 7 in which said passages which areintersected by said indentation are blind passages which communicatewith said one surface only through the associated intersectingindentation.

9. A unitary two-sided flat ceramic block for emission of infra-red raysby heating one side of said block by the combustion at said side of agas mixture flowing from the other side through a great many continuouselongated passages each of which is straight over at least most of itslength all having substantially the same cross-sectional area at leastat their inlet ends adjacent said second side of said block and beingsubstantially evenly distributed over the area of said block, saidceramic block at its one side having a repeat pattern of indentationsextending below the outer surface of said one side, each of saidindentations intersecting the ends of at least two of said passages togather the outflow of at least two of said passages, at least some ofsaid passages being partly obturated along their axial length by theceramic material of said block to thereby increase the velocity of saidgas mixture in said restriction and to impart to said gas mixture aturbulence adjacent the outlet end of said restriction, the arrangementof said passages and their dimensions together with the shape and sizeof said indentations comprising a means which is jointly operable tocause at least some of the gas mixture to burn at least in part atsubstantially the outlets of said obturation, the thickness of saidblock at its minimum within said indentations and the nature of therefractory material of said block comprising a means which is jointlyoperable to prevent said first surface from reaching the ignitiontemperature of said gas mixture, and each said passage being many timeslonger than its width and sufficiently narrow to prevent the flame fromback-propagating therethrough to said first surface.

10. The invention as described in claim 9 in which the repeat pattern ofindentations comprises a plurality of parallel slots in said one side ofsaid block, said cuts intersecting said passages at or near their axis.

1 1. The invention as described in claim 9, in which said first-namedside comprises alterations of straight bored passages lined in rows andsaid indentations comprise slots joining several passages in alternaterows.

12. The ceramic block of claim 10' in which said partial passageobturation occurs along the axial length of each said passage at a pointbetween said one surface and the bottom of the intersecting slot.

13. The ceramic block of claim 12 in which each said slot is formed overthe deepest part of its depth of substantially parallel planar surfaceseach said slot having opposing surfaces at its upper portion adjacentsaid one surface which are significantly Wider spaced than at the pointof intersection of said slot with said passages.

14. A radiant grid element for a gas burner comprising,

a unitary block of refractory heat insulating material having a myriadof minute-bore passages which extend from an inlet end at a firstboundary surface of said block toward the opposite sunface of said blockfor conducting from said first surface a myriad of streams of acombustible gas mixture for combustion adjacent said opposite surface,said block having formed in said opposite surface a repeat pattern ofindentations each of which intersects at least two of said passages,

each said indentation having opposing peripheral walls whose spacing atthe bottom of said indentation is less than the maximum cross-sectionaldimension of an intensected passage but whose spacing adjacent saidopposite surface is greater than said maximum cross-sectional dimension,said change in spacing of said opposing peripheral walls beingdiscontinuous to thereby form a step which increases the turbulence ofthe burning gas mixture adjacent said opposite sunface, the thickness ofsaid block at its minimum within said cavities and the nature of therefractory material of said block comprising a means which is jointlyoperable to prevent said first surface from reaching the ignitiontempenature of said gas mixture, and each said passage being many timeslonger than its width and sufficiently narrow to prevent the flame fromback-propagating therethrough to said first surface.

15. The radiant grid element of claim 14 in Which at least some of saidindentations have opposing peripheral wall surfaces which aresubstantially parallel in the area adjacent to the intersection of saidindentation with said passages but thereafter diverge in the regionadjacent the furthest reaches of said opposite surface.

16. A radiant grid element for a gas burner comprising,

a unitary block of refractory heat insulating material having a myriadof minute-bore passages which extend from an inlet end at a firstboundary surface of said block toward the opposite surface of said blockfor conducting from said first surface a myriad of streams of acombustible gas mixture for combustion adjacent said opposite surface,said block having formed in said opposite surface a great many discreteprotwberances which are substantially uniformly spaced bothlongitudinally and tnansversely over said opposite surface, each saidprotuberance being formed at least in part by upstanding walls whichextend upwardly and inwardly above a lower portion of said oppositesurface, at least some of said passages opening at least in part intosaid lower portion and others of said passages opening at least in partinto said upstanding walls,

the arrangement of said passages and their dimensions together with theshape and size of said discrete pr-otuberances comprising a means whichis jointly operable to cause at least some of the gas mixture to burn atsubstantially said lower portion of said opposite surface,

said upstanding walls of said discrete protwberances being contacted bythe flames of the burning gas mixture,

the thickness of said block at its minimum and the nature of therefractory material of said block comprising a means which is jointlyoperable to prevent said first surface from reaching the ignitiontemperature of said gas mixture, and each said passage being many timeslonger than its width and sufficiently narrow to prevent the flame fromback-propag ating therethrough to said first surface.

17. The radiant grid element of claim 16 in which adjacent of saidprotuberances have side walls which generally face each other, said sidewalls being heated substantially to incandescence by said flames of theburning gas mixture and thereby providing mutually reverberatinginfra-red radiating surfaces which aid in the complete combustion ofsaid gas mixture.

18. A radiant grid element for a gas burner comprising,

a unitary block of refractory heat insulating material having a myriadof substantially straight minute-bore passages which extend from aninlet end at a first boundary surface of said block toward the oppositesurface of said block for conducting from said first surface a myriad ofstreams of a combustible gas mixture for combustion adjacent saidopposite surface,

said opposite surface being formed in part by a repetitive pattern ofmutually intersecting elongated longitudinal and transverse indentationsat least some of which have a plurality of said passages opening atleast in part into theirxbottom portions.

said indentations being at least for the most part substantiallyuniformly spaced in both the longitudial and transverse directions overthe opposite surface of said block, the arrangement of said passages andtheir dimensions together with the shape and size of said intersectingindentations comprising a means which is jointly operable to cause atleast some of the gas mixture to burn at substantially the bottoms ofthe respective indentations, said intersecting indentations having sidewalls which slope upwardly and outwardly over at least a portion oftheir length at an acute angle to the longitudinal axes of said passagesto form in said opposite surface a plurality of raised portions joinedwith the remainder of said opposite surface by upstanding surfaces whichare heated to incandescence Iby the flames of combustion of said gasmixture,

adjacent of said discrete raised portions having respectively opposingsloping surfaces to enhance mutual infra-red radiation therrebetween.

the thickness of said block at its minimum within said indentations andthe nature of the refractory material of said block comprising a meanswhich is jointly operable to prevent said first surface from reachingthe ignition temperature of said gas mixture,

and each said passage being many times longer than its width andsufficiently narrow to prevent the flame lfrom backpropagatingtherethrough to said first surface.

19. A radiant grid element for a gas burner comprising, a unitary blockof refractory heat insulating material having a myriad of minute-borepassages: which extend from an inlet end at a first boundary surface ofsaid block toward the opposite surface of said block for conducting fromsaid first surface a myriad of streams of a combustible gas mixture forcombustion adjacent said opposite surface, said opposite surface beingdefined by a repetitive pattern of elemental portions which are raisedrelative to depressed portions of said opposite surface and in partextend to the outermost reaches of said opposite surface, said raisedportions and said depressed portions being joined by upstandingsurfaces, some of said passages opening at least in part into saidraised elemental areas at their said outermost portions and defining aline of intersection with the respective raised elemental portion whichfor at least most of it length lies in the same plane and others of saidpassages opening at least in part into said depressed portions each ofsaid passages which opens into one of said naised portions beingsurrounded at least in part by at least one of said depressed portionsinto which at least one of said passages opens, said passages which openinto said depressed portions providing combustion fiames and hot gaseswhich pass over said upstanding surfaces to increase their temperaturemarkedly and thereby facilitate the combustion of said gas mixture at adeep level within said passages which open into said raised areas, thearrangement of said passages and their dimensions causing at least someof the gas mixture to burn at substantially the point of emergence ofsaid passages into said depressed portions, the thickness of said blockat its minimum within said cavity and the nature of the refractorymaterial of said block comprising a means which is jointly operable toprevent said first boundary surface from reaching the ignitiontemperature of said gas mixture, and each said passage being many timeslonger than it width and sufiiciently narrow to prevent the flame fromback-propagating through to said first surface.

20. A radiant grid element for a gas burner as defined in claim 14 inwhich said indentations alternate with raised areas which extend to theoutermost reaches of said opposite surface and with at least some ofsaid raised areas having passages opening thereinto.

21. A radiant grid element for a gas burner as defined in claim 19 inwhich at least some of said upstanding surfaces generally face eachother and are generally parallel to the axes of said passages.

22. A gas burner having a radiant grid element comprising, a unitaryblock of refractory heat insulating material having a myriad ofminute-bore passages which extend from an inlet end at a first boundarysurface of said block toward the opposite surface of said block forconducting from said first surface a myriad of streams of a combustiblegas mixture for combustion adjacent said opposite surface, said oppositesurface being defined by .a repetitive pattern of elemental portionswhich are raised relative to depressed portions of said opposite surfaceand in part extend to the outermost reaches of said opposite surface,said raised portions and said depressed portions being joined byupstanding surfaces which are substantially parallel to the axes of saidpassages, some of said passages intersecting said depressed portionsover only a part of their cross-section and others of said passagesopening at least in part into said raised portions, said passages whichopen into said depressed portions providing combustion flames and hotgases which pass over said upstanding surfaces to increase theirtemperature markedly and thereby facilitate the combustion of said gasmixture at a deep level within said passages which open into said raisedareas, the arrangement of said passages and their dimensions causing atleast some of the gas mixture to burn at substantially the point ofemergence of said passages into said depressed portions, the thicknessof said block at its minimum within said cavity and the nature of therefractory material of said block comprising a means which is jointlyoperable to prevent said first boundary surface from reaching theignition temperature of said gas mixture, and each said passage beingmany times longer than its Width and sufiiciently narrow to prevent theflame from back-propagating through to said first surface.

References lifted by the Examiner UNITED STATES PATENTS 1,308,364 7/1919Lucke 158-99 1,313,196 8/1919 Locke 15899 1,326,767 12/ 1919 Moore.1,901,086 3/1933 Cox 158116 2,215,079 9/1940 Hess 15899 3,179,155 4/1965Partiot 158116 FOREIGN PATENTS 551,940 11/1956 Belgium, 558,007 6/1957Belgium. 71,572 7/1959 France. 485,086 10/1929 Germany. 601,249 1/1960Italy.

FREDERICK L. MATTESON, JR., Primary Examiner.

JAMES W. WESTHAVER, Examiner.

H. B. RAMEY, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,321,000 May 23, 1967 Maurice Partiot It is certified that errorappears in the above identified patent and that said Letters Patent arehereby corrected as shown below:

Column 5, line 26, "cavities" should read Column 7, line 9, "cavity"should read indentations depressed portions Column 8, line 12, "cavity"should read depressed portions Signed and sealed this 2nd day ofSeptember 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. E. JR.

Attesting Officer Commissioner of Patents

1. A RADIANT GRID ELEMENT FOR A GAS BURNER COMPRISING, A UNITARY BLOCKOF REFRACTORY HEAT INSULATING MATERIAL HAVING A MYRAID OF CONTINUOUS,STRAIGHT MINUTE-BORE PASSAGES WHICH EXTEND FROM AN INLET END AT A FIRSTBOUNDARY SURFACE OF SAID BLOCK TOWARD THE OPPOSITE SURFACE OF SAID BLOCKFOR CONDUCTING FROM SAID SURFACE OF MYRAID OF STREAMS OF A COMBUSTIBLEGAS MIXTURE FOR COMBUSTION ADJACENT SAID OPPOSITE SURFACE, SAID BLOCKHAVING FORMED IN ITS SAID OPPOSITE SURFACE A REPEAT PATTERN OFINDENTATIONS EACH OF WHICH INTERSECTS AT LEAST TWO OF SAID PASSAGES,EACH SAID INTERSECTED PASSAGE TOGETHER WITH THE RESPECTIVE INTERSECTINGINDENTATION FORMING A RESTRICTION IN THE FLOW PATH OF SAID GAS MIXTUREPRIOR TO ITS EMERGENCE INTO THE ASSOCIATED INDENTATION TO THEREBYINCREASE THE VELOCITY OF SAID GAS MIXTURE IN SAID RESTRICTION AND IMPARTTO SAID GAS MIXTURE A TURBULENCE ADJACENT THE OUTLET END OF SAIDRESTRICTION, THE ARRANGEMENT OF SAID PASSAGES AND THEIR DIMENSIONSTOGETHER WITH THE SHAPE AND SIZE OF SAID INDENTATIONS COMPRISING A MEANSWHICH IS JOINTLY OPERABLE TO CAUSE AT LEAST SOME OF THE GAS MIXTURE TOBURN AT SUBSTANTIALLY THE OUTLET ENDS OF THE RESPECTIVE RESTRICTIONS,THE THICKNESS OF SAID BLOCK AT ITS MINIMUM WITHIN SAID INDENTATIONS ANDTHE NATURE OF THE REFRACTORY MATERIAL OF SAID BLOCK COMPRISING A MEANSWHICH IS JOINTLY OPERABLE TO PREVENT SAID FIRST SURFACE FROM REACHINGTHE IGNITION TEMPERATURE OF SAID GAS MIXTURE, AND EACH SAID PASSAGEBEING MANY TIMES LONGER THAN ITS WIDTH AND SUFFICIENTLY NARROW TOPREVENT THE FLAME FROIM BACK-PROPAGATING THERETHROUGH TO SAID SAID FIRSTSURFACE.